import java.util.Scanner;

public enum Color {
    RED, GREEN, BLANK, YELLOW ;

}

class TrafficLight {
    //Color color = Color.BLANK;
    public void change(Color color) {
        switch (color) {
            case RED:
                color = Color.GREEN;
                break;
            case YELLOW:
                color = Color.RED;
                break;
            case GREEN:
                color = Color.YELLOW;
                break;
        }
        System.out.println(color);
    }
}

class TestEnum{
    public static void main(String[] args) {
        Color[] values = Color.values();
        for (Color c : values){
            System.out.println(c);
        }
    }
}
